Posted by jrbecker on January 16, 2006, at 9:33:41
don't know what bearing this has on thyroid augmentation for affective disorders...
http://www.pharmalive.com/news/index.cfm?articleid=305569&search=1
To Treat or Not to Treat: New Data Says a Mild Case of Underactive Thyroid Disease Should Be Left Alone
New Study Contributes to Ongoing Controversy
CHEVY CHASE, Md., January 12, 2006 /PRNewswire/ -- Weighing in on the controversy of whether to treat a person with mild hypothyroidism -- or an underactive thyroid -- with thyroid hormone, Norwegian researchers found strongly in favor of no treatment, according to a placebo-controlled, double-blind intervention study published in the January issue of The Journal of Clinical Endocrinology & Metabolism published by The Endocrine Society.
People with no obvious symptoms but with thyroid-stimulating hormone (TSH) levels of 3.5 - 10.0 mIU/L and normal free thyroxine (T4) and free triiodothyronine (T3) levels in the blood -- the standard definition of subclinical hypothyroidism -- had no significant differences in cognitive function and hypothyroid symptoms when compared to a healthy control group."Moreover," said lead author Dr. Rolf Jorde, of University Hospital of North Norway in Tromso, Norway, "in the intervention arm of the study, treatment with the thyroid hormone thyroxine had no significant effect on these parameters as well."
Classic symptoms of hypothyroidism include fatigue, depression, weight gain, and infertility. According to the researchers, in people who have these obvious symptoms coupled with elevated TSH above 10.0 mIU/L and low free T4, the decision to start treatment with thyroxine is usually easy. However, whether to treat people with a mild form of hypothyroidism is the subject of an ongoing controversy, primarily because of the lack of definitive research, especially when it comes to neuropsychological effects, symptoms, and the effect of thyroxine.
"More than 27 million Americans have overactive or underactive thyroid glands," said Leonard Wartofsky, MD, President-Elect of The Endocrine Society. "January is Thyroid Awareness Month, and this year we're focusing on encouraging people to know their numbers. Finding out TSH and T4 numbers through a simple blood test will flag any imbalances -- information a doctor can use to treat significant problems." He added, "If your thyroid isn't working properly, then neither are you."
To appropriately study this issue, the researchers ensured that the participants were not aware of their thyroid status, thereby not recruiting them from clinical practice. Dr. Jorde and colleagues used the research opportunity provided by the Tromso epidemiological health survey, which was performed for the fifth time in 2001. The Tromso study is composed of all willing men and women older than 29 years living in Tromso who participated in the second phase of the fourth Tromso study or who became 30, 40, 45, 60, or 75 years old during 2001.
As part of the survey, TSH was measured in the 7,954 participants. After exclusions, there were 363 people with a TSH level between 3.5 and 10.0 mIU/L. Those who were excluded included people with serious medical conditions, on thyroid medication, above the age of 80, and who declined to participate. The remaining 249 people were invited to undergo a follow-up examination. Of these, 89 - 45 men and 44 women -- fulfilled the criteria for subclinical hypothyroidism. For each person with subclinical hypothyroidism invited to participate in the follow-up study, another person of the same age and sex, with a TSH between 0.50 - 3.49 mIU/L, was randomly selected from the Tromso study to serve as a control. Those who agreed to participate included 154 people -- 72 men and 82 women. The invitation letters informed the subjects about the purpose of the study but did not disclose anyone's thyroid status. All participants underwent a clinical examination, answered a questionnaire about hypothyroid symptoms, and underwent neuropsychological tests to assess cognitive and emotional function, including well-being and mental health. During these tests, the examiners were blinded to the TSH status of the participants.
After this phase of the study, the participants were informed about their thyroid status. Those with subclinical hypothyroidism were invited to participate in a 12-month intervention study. The 69 who consented were randomly selected to receive either a placebo or thyroxine. During the first six weeks, the thyroxine group received 50 ug daily and, for the following six weeks, they each received 100 ug daily. Thereafter, the thyroxine dose was given according to a person's TSH levels. Their blood was tested for TSH, free T4, and free T3 at three, six, nine, and 12 months. After 12 months, the participants answered a questionnaire that focused on changes in symptoms since the first visit. The neuropsychological tests also were repeated.
Cognitive symptoms like slow mental activity, reduced memory function, and the inability to concentrate are frequently reported in people with overt hypothyroidism and also in some studies on subclinical hypothyroidism. However, no significant differences in cognitive function or hypothyroid symptoms were found between the subclinical disease and control groups.
Similar to cognitive function, there is a previously established association between overt hypothyroidism and depression. In addition, features of depression have been reported more frequently in subclinical hypothyroidism, with a slight improvement after thyroxine treatment, although some studies have shown this connection to be weak. In this study, however, those with subclinical hypothyroidism scored more favorably than the controls when emotional function was assessed.
Moreover, in the intervention phase of the study, thyroxine had no effect on cognitive function or depression, so much so that most of the participants thought they had received a placebo.
The researchers noted several weaknesses with their study, primarily stemming from the difficulty of finding a large group of people with subclinical hypothyroidism who are not aware of their thyroid status. They wrote, "We cannot rule out that we would have found significant differences between the subclinical hypothyroid and control group had we included more subjects. However, to include 89 subjects with subclinical hypothyroidism, we had to screen almost 8,000 subjects and a larger group would be hard to find."
On the other hand, they acknowledged their study's considerable strengths. "We applied a broad range of tests and used strict selection criteria for both subclinical hypothyroidism and control subjects. Those included were recruited from an epidemiological survey and not from clinical practice, which would have favored inclusion of subjects with symptoms unrelated to thyroid diseases."
This study was supported by a grant from the Norwegian Research Council and The Northern Norway Regional Health Authority. The thyroxine and placebo tablets were supplied by NycoMed Pharma.
Founded in 1916, The Endocrine Society is the world's oldest, largest, and most active organization devoted to research on hormones, and the clinical practice of endocrinology. Endocrinologists are specially trained doctors who diagnose, treat and conduct basic and clinical research on complex hormonal disorders such as diabetes, thyroid disease, osteoporosis, obesity, hypertension, cholesterol and reproductive disorders. Today, The Endocrine Society's membership consists of over 12,000 scientists, physicians, educators, nurses and students, in more than 80 countries. Together, these members represent all basic, applied, and clinical interests in endocrinology. The Endocrine Society is based in Chevy Chase, Maryland. To learn more about the Society, and the field of endocrinology, visit the Society's web site at http://www.endo-society.org
CONTACT: Tadu Yimam of The Endocrine Society, +1-301-941-0251, or tyimam@endo-society.org
Web site: http://www.endo-society.org/
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